CVE-2026-70626: nltk Link Following
Vulnerability summary
CVE-2026-70626 is a high (CVSS 8.6) Link Following vulnerability in nltk. EPSS estimates a 0.20% chance of exploitation in the next 30 days, higher than 9.2% of scored vulnerabilities. 1 public exploit is recorded.
Timeline
- 22-08-2026PublishedVulnerability first disclosed.
- 24-08-2026Last modifiedVulnerability information updated.
Description
NLTK versions before 3.9.4 contain a symlink escape vulnerability in CorpusReader.open() that allows local attackers to read arbitrary files outside the corpus root. The vulnerability exists because path validation is lexical and does not account for symlink resolution, enabling attackers to place symlinks inside the corpus root to access files outside the intended boundary.
CVSS metrics
8 scores · 5 sources · 2 versions- OSV · PypiEcosystem advisory · calculated8.6HighCVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
- OSV · UbuntuEcosystem advisory · calculated8.6HighCVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
- OSV · DebianEcosystem advisory · calculated8.6HighCVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
- NVDNIST8.6HighCVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
- OSV · UbuntuEcosystem advisory · calculated6.2MediumCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
- NVDNIST6.2MediumCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
EPSS trend
Probability
0.20%
Chance of exploitation in the next 30 days
Percentile
9%
Versus all other CVEs
30-day change
-0.01 pp
From 0.21% on 20-09-2026
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
1 foundNltk
Maturity: poc
Weaknesses
CWE · root causeAffected systems
Debian1 product
- nltkAll versions (No fix recorded) | < 3.10.0-1
Nltk1 product
- nltk< 3.9.4
PyPI1 product
- nltk< 3.9.4
Ubuntu1 product
- nltkAll versions (No fix recorded)
4 vendors · 4 products
References
15 links- www.vulncheck.com/advisories/nltk-before-symlink-escape-via-corpusreaderThird Party AdvisoryWEBAdvisoryREPORTVendor Advisory
- github.com/nltk/nltkPACKAGE
